A grid-connected photovoltaic (PV) system refers to a power network incorporating a solar energy battery array or a photovoltaic power station into a grid so as to realize power supply. A Low Voltage Ride Through (LVRT) refers to a case as follows: when a voltage dip occurs in the power network of the grid-connected PV system, a DC (direct-current) side, such as the photovoltaic power station, can remains a connection with the grid at an AC (alternating current) side, a DC voltage from the DC side is converted into an AC voltage for the grid at the AC side by an inverter(s) until the malfunction in the grid is removed, so that a voltage dip period is ridden through, such that the malfunction in the grid can be prevented from expanding and the reliability of the power supply can be enhanced. The voltage dip refers to a sudden event of which a duration is extremely short and during which a Root Mean Square (RMS) value of the voltage on a bus bar decreases sharply and rapidly.
When a power supply proportion of the photovoltaic power station or the solar energy battery array is high in the power network and their penetration rate is also high, if the photovoltaic power station is split in a passive protection manner by which the photovoltaic power station is removed immediately from the power supply network as the voltage dip occurs, an active power generation would decrease greatly, such that the power supply system is difficult to be recovered, and even splitting of other units may be caused, which may lead to a power cut in a large scale and expand malfunctions. In this case, an ability of Low Voltage Ride Through is necessary.
In existing method and apparatus for controlling the Low Voltage Ride Through of the photovoltaic grid-connected inverter, controlling for an output current of the inverter is ignored, such that problems that distortions caused by fluctuations in the current are serious and quality of the outputted electric energy is affected severely when the voltage dips rapidly, therefore the existing method and apparatus for controlling the Low Voltage Ride Through of the photovoltaic grid-connected inverter are required to be further optimized and improved.